Andrea Leadsom insisted she believed that everyone has an equal stake in society, after he controversial comments on being a mother

Andrea Leadsom is facing a "black-ops" campaign by MPs who want to "denigrate her reputation" , key supporter Iain Duncan Smith has claimed.

It comes after allies of Theresa May stepped up their criticism of Mrs Leadsom, with one senior minister suggesting she could become the Tory equivalent of Jeremy Corbyn because of her lack of support in Parliament.

Employment minister Priti Patel, who campaigned for Brexit alongside Mrs Leadsom, suggested that the energy minister lacked the experience and broad appeal to win a general election.

But former Tory leader Mr Duncan Smith insisted both candidates are capable of becoming the next prime minister and called for the Conservative Party to show decency during the campaign.

Asked about reports that some MPs are prepared to quit the party if Mrs Leadsom become Prime Minister, he told ITV's Peston on Sunday: "I have a simple comment to them, which is calm down for God's sake, this is a leadership election and I think people come to regret some of the silliest things they say during a leadership election.

"I've seen it all before - the reality is that both of them are qualified.

"Look, if Andrea was so unqualified to be Prime Minister, and you know we've had a lot of sniping, a kind of real 'black-ops' operation to denigrate her reputation.

"If she was so bad what in heaven's sake would the Prime Minister be doing making her a serious government minister?"

He later added: "We should really be very careful about the threats and the things that we say, all of us, and conduct this in decency."

Ms Patel, who is backing Mrs May's campaign, warned that Mrs Leadsom could find herself unable to govern due to the lack of support from MPs, or win an election victory by appealing to swing voters.

In an interview with the Sunday Telegraph, she said: "You win elections by having that broad appeal.

"Look at Labour right now, and the narrow appeal they have. We have to represent society as it is today and be a true voice for modern Britain and a positive Britain."

Mrs May secured her place on the leadership ballot by securing 199 votes from MPs, with Mrs Leadsom winning the support of 84 colleagues.

Ms Patel warned a victory for Mrs Leadsom could mean that the process of leaving the European Union would be harder to deliver, even though the energy minister backed Brexit and Mrs May had supported a vote to Remain in the EU.

"We have to govern," Ms Patel said. "To govern we have got to be able to carry the support of Members of Parliament. That's incredibly important. I don't need to give a re-run of what's happening with Labour right now."

Asked if Mrs Leadsom could become a Conservative version of Mr Corbyn, Ms Patel said: "We could end up in that situation. And then it becomes very difficult to govern and deliver the programme for Leave."

She added: "Right now we need an individual with a great deal of experience. She doesn't have that just yet, not yet. She is in government - but Theresa's experience is second to none."

She added that Mrs May was "on a par" with former prime minister Mrs Thatcher, the first female occupant of Number 10.

Ms Patel's comments came after Mrs Leadsom endured a barrage of criticism after appearing to suggest that being a mother gave her an advantage over her childless rival.

Mrs Leadsom said she was "disgusted" by the way her comments had been presented and insisted that she believed "everyone has an equal stake in our society", stressing that she did not want the issue of children to be a feature of the campaign.

In an interview with The Times, Mrs Leadsom said: "Genuinely I feel that being a mum means you have a very real stake in the future of our country, a tangible stake."

The Home Secretary has previously spoken about how she and husband Philip were affected by being unable to have children.

Mr Duncan Smith suggested the interview was a "stitch-up".

He told Robert Peston: "I've been around in politics long enough to see plenty of incredibly experienced cabinet ministers and Prime Ministers get stitched up in the course of an interview..."

He added: "The question really was did Andrea at any stage really believe that she was in the business of trying to contrast her family background with Theresa's and I don't believe that.

Mrs May's campaign chief, Brexit-backer Chris Grayling, insisted that there was "no question" of a second referendum on the EU if the Home Secretary won, with the UK severing ties with Brussels before the 2020 general election.

He said that he was expecting EU citizens to be able to remain in the UK after Brexit, something Mrs May has refused to guarantee unless she receives a similar commitment from the other 27 member states about the future rights of Britons overseas.

"I don't think there will be any change on either side," he said. "I think everyone will take a grown-up approach to this. It would be too damaging to do otherwise. However, we should always make sure that we look after the interests of our own citizens. I don't think anything is going to change."

He added: "I'm expecting all EU citizens, perhaps bar those who've committed criminal offences and ones with individual circumstances, to be able to stay as they do now. And I'm expecting UK citizens in other countries to be able to stay there too. That's right and proper."

He told the BBC's Sunday Politics she had stressed that "Brexit means Brexit" and added: "We think she has got the weight and the experience to deliver what people want."

He added: "She's said that we will trigger Article 50 around the end of this year. There is then a two-year timeframe and the next general election is 2020. So I can't see any circumstances in which we wouldn't have (left) by 2020."

Mrs Leadsom's campaign chief Tim Loughton responded to suggestions that she would struggle to bridge divides in the party by saying either candidate would have a "big job of work to do" to unite the party after the EU referendum.

He told Sky News' Murnaghan programme: "Andrea is actually a really nice person, widely liked within the Conservative party and widely respected across the whole of the House of Commons so she has form when it comes to bringing people together."

He dismissed the row over Mrs Leadsom's Times interview: " The thing with Andrea, she is a very genuine person and she gave an interview to a very experienced journalist with the Times who clearly wanted to lead her down a path and she kept going on relentlessly about the children issue...."

He said Mrs Leadsom had made it "clear right through this campaign, that we are not running any negative stuff, in no way is our campaign about undermining the other candidates and is about the positive case for why Andrea will be the best candidate for Prime Minister.

"She is fired up, what makes her passionate in politics is her children and her family, since when has it been a crime to be proud about your children and today we just heard Andy Murray saying what fires him up is his children, so is he being critical of other tennis players as well?"